Hi, I also released my Prom replacements.One with invisible eprom on the bottom and one for development.Both have the option to take a 4K ROM F000.FFFF (e.g. Krusader)Gerbers are here: https://github.com/vossi1/Apple1-prom-replacement
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Huge thanks, I have 2 Apple I blanks that will take advantage of this (one for the 6800, one for a 6502).
Very nice.
Cypress CY7C150 seem to be fairly easy to get combined with a 74HCT4040 Binary Counter it should be able to replace 4x 2504.
An adapter PCB that plug into the socket C4 and also holds the 74157 that belongs there should handle D5A/B and D4A/B.
Maybe it is possible to keep this adapter universal so you can also plug it into C14 where it will handle D14A/B and with a two pin breakout connector to C11B and handle the cursor.
An adapter board that plugs in A9, A10 and A11 can grab most of the signals for a DRAM replacement If I did not miss anything we need a jumper wire to what ever bridges to X in the patch field.
CY7C171A/CY7C172A seam to be a quite good fit but would need latches to decode row and column address phase. Attaching some more modern SRAM direct to the CPU would be far easier.
With all the replacements it would be a fully single voltage 5V only version.
A 74HCT393 might be even a better then the 74HCT4040
Very good job!. I used a PROM adapter for the 2716 EPROM myself.Recently, however, I managed to buy a number of Soviet PROMs and built a simple, manual programmer for them using switches. It works – watch the video.
https://www.youtube.com/watch?v=p6M5ABbfTHk
Also, Tesla MH74S287 PROMs are widely available in Europe, and simple programmers are also available for them. I happily use Tesla Memories in my Apple 1, ACI, etc. replicas.
Regards
Mateusz